


It Was Just a Prank

by ZAMBOT_3



Category: Ben 10 Series
Genre: Body Hair, Cousin Incest, Creampie, F/M, First Time, Incest, Loss of Virginity, female body hair
Language: English
Status: Completed
Published: 2019-12-13
Updated: 2019-12-13
Packaged: 2021-02-26 23:00:13
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,664
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21776989
Author URL: https://archiveofourown.org/users/ZAMBOT_3/pseuds/ZAMBOT_3
Summary: Ticked off over how long his cousin takes in the bathroom Ben hatches a plan to ruin her morning routine, but when Ben's prank has an unaffected side effect in how much sexier it makes his cousin, he starts getting very hot and bothered and not just because of the Indian Summer.
Relationships: Ben Tennyson & Gwen Tennyson, Ben Tennyson/Gwen Tennyson
Comments: 3
Kudos: 65





	It Was Just a Prank

**Author's Note:**

> This was a commission for a good friend ^^ You can find my commission information on my Twitter: 
> 
> https://twitter.com/NsfwSwindle
> 
> my commission queue is currently open! So get yourself a commission before those slots fill up!!

The Tennyson cousins had a bad habit of getting on each other’s nerves, and while this is not altogether uncommon for family, especially siblings, there was something else that separated them. It was almost imperceptible to their young minds, as inexperienced as they were, but the charge they experienced when alone together was impossible to ignore and it was dealt with through arguments and fighting more often than not. Ben for one didn’t care to understand why they were always at each other's throats, but after one too many snide remarks he needed to do something to shut his cousin up for good, or at least a long while. Ben stewed with this thought for a few days, what would be the most effective way to get back at Gwen, eventually deciding that anything he could do to disrupt the notoriously cranky girl’s morning routine would have the desired effect.  Ben had been locked out of his Grandpa Max’s guest bathroom far too often because of how long his cousin spent in the bathroom, but from that he had learned how frequently she shaved. Apparently Gwen had become quite obsessed with keeping her skin smooth and hairless, made very evident by the mess of razors and skincare product she left out every morning on the bathroom counter, and once that had been figured out Ben’s plan came together. 

Ben Tennyson was no stranger to pranks, but if he wanted a really good one then he’d need some assistance from his watch, specifically Greymatter. Only a few seconds of brainstorming and he had his plan of action, there were several chemical combinations that when added together could encourage hair growth and should these be discreetly added into her shaving cream then every time she shaved the hair she removed would come back with a vengeance. The most difficult part was finding the time to enact his plan, with the need to synthesize the ingredients from items all over the house, he had to wait until both Gwen and Max were out of the house and when he finally was alone he would have to be very quick lest his watch time out before he could finish the procedure. 

Finally, on Sunday, Grandpa Max had to go grocery shopping and Gwen eagerly volunteered if only to get away from her annoying dweeb of a cousin. Regardless of her reason, it provided Ben the chance he finally needed and with a list of the supplies he had already drawn up, he darted between the bathroom and kitchen to set up a makeshift lab in order to prepare his chemical concoction. With everything finally together he transformed into his Galvan alter-ego and went to work. Greymatter rushed from makeshift beaker to bottle, his size proving to be his greatest hindrance. Still, without Galvan intellect Ben would have no way of doing this and even then he didn’t understand what or how he was doing it, the Galvan mental process being so far advanced beyond Ben’s own that he had no way of parsing the surge of information and mental processing. In an exhaustive 15 minute sprint, Ben finished the job, transforming Gwen’s shaving cream into a hair growth stimulant that would still provide a smooth and close shave. Panting, Ben hurried to remove the evidence of his project and replaced Gwen’s shaving cream and the rest of his ingredients with time to spare and spent the rest of his time trying to clean and replace the dishes he had to use.  When the front door opened and announced Gwen and Max’s return, Ben tried his best to appear casual but Gwen saw through his act immediately.

“What’s that weird look about?” She asked with her arms crossed and her hip swayed to the side in a pose clearly rehearsed to properly convey her annoyance. 

“I’ve got no idea what you’re talking about.” Ben replied, not trying very hard to look innocent.

Gwen’s eyes narrowed in suspicion, but before she could press him Grandpa Max called for them from the kitchen, “If you two are through bothering each other I could use some help carrying these groceries in."

“Coming, Grandpa!.” Ben shouted, leaving Gwen in the living room.

Gwen huffed in frustration, knowing she would have to set aside this investigation for later; she knew Ben wasn’t as smart as her but he was not without his surprises. While they put up the groceries Ben tried hard to not laugh at his cousin as he envisioned her shock and surprise when his prank finally came to fruition, each time he caught a glimpse at her he had to suppress laughter lest she realize something was amiss. As she stood on her tiptoes and reached to put a box in the cabinet, he imagined how her pits would start growing her pretty pretty red hair. He pushed that thought aside to keep himself from busting a gut, but her hair  _ was  _ very pretty he had to admit. Ben had noticed he had somewhat of a preference for redheads, but lots of guys felt the same way and even if she was his cousin he could admit her hair looked nice, there was nothing wrong with that. 

For the rest of the evening their usual sniping was kept at a minimum with Ben trying to keep his distance lest he somehow give away his prank. Ben’s stoic exterior was tested however anytime Gwen got up to do anything, his eyes were drawn to her, telling himself that it was too make sure she was not growing wise to his scheme. His eyes were particularly glued to her as she messed with an extension chord. As Gwen bent over Ben lowered his comic slightly, staring at her rear which looked deliciously shapely in her white skinny jeans. When he realized what and who he had unconsciously begun ogling he snapped his attention back to his reading material and chastised himself for staring off into space like some sort of doofus, no way had he been looking at his cousin’s ass, not at all. 

The next morning Ben couldn’t help but smile as he was locked out of the bathroom for an hour as usual and tried hard to act as usual when Gwen finally stepped out.

“Would it kill you to wear clothes around the house, or at least shut your door?” Ben asked as he passed her bedroom. She was sitting on the edge of her bed in just a towel as she clipped her nails. The towel she had wrapped about her was hanging a little low on her chest, something Ben zeroed in on immediately. 

“Bite me dweeb, don’t you have anything better to do than ogle your cousin?” Gwen replied, not even looking up from what she was doing.

  
  
“I wasn’t-!” Ben started, face flushing red before simply walking away from the conversation, taking solace in the fact that his prank would soon make itself apparent.

  
  


The following day Gwen rushed to the bathroom even quicker than usual, and with some satisfaction Ben noted how it took her even longer than usual to finish up. Usually he would try to rub something like this in, but he had to lay low, this was a prank with longevity and if he were to give himself away who knew how much trouble he’d get into with Grandpa Max. As much as it pained him to not bother his cousin Ben kept to himself as Gwen did the same, obviously not in the mood to start anything with him. The next day it was much the same, Gwen rushed into the bathroom and stayed for quite some time. It was on the fourth day that Ben came to a realization, while he could almost definitely find a way to reverse what he had done to her, how exactly would he fess up to what he’d done and not get in huge trouble. As far as Ben was concerned a prank had failed if the person you're pranking doesn't realize what you'd done and as far as Gwen knew this could very well be some sort of natural phenomena and if that's the case he hadn't gotten even with her at all. Ben supposed he could admit what he had done to her, it was clearly bothering her and there would be some satisfaction when he saw the look on her face, but there was no scenario in which he did that and didn't get into huge trouble with Grandpa Max. Ben had trouble thinking ahead sometimes, but this took the cake, all his planning and busting his butt creating his hair growth formula, and it was all for nothing.

For the rest of the week Ben was more or less deflated, his prank having essentially no conclusion or ‘Gotcha’ moment. Gwen meanwhile seemed to grow more and more comfortable with the changes Ben had caused by the day. She was spending less time in the bathroom until eventually her morning routine returned to its original length, perhaps even a bit shorter. Gwen began to spend less time in her room and more time bothering Ben as before with every glimpse of hair peeking from beneath her pant leg or under her sleeve causing a surge of regret, and an additional feeling he didn’t want to acknowledge. Ben remained awkward as he and Gwen traded barbs, particularly when any evidence of what he’d done to her was apparent, but after a week things between them had returned to its usual slightly volatile balance and he could almost forget he had tried to prank her in the first place. 

It was the last week of summer when everything would come back to bite Ben. Gwen had regained full confidence in her body by this time and had taken to crop tops and shorts as befit the hot and humid summer weather, but her efforts to cool herself down only made Ben even more hot and bothered. Ben had fought hard to get to choose the T.V. station but he wasn’t even paying attention to it, his cousin who was busy reading on the couch made for better observation. Her low-waisted shorts offered the most tantalizing view of the orange trail leading up her navel as well as how much the hair along her legs spread. On occasion she would adjust her position and the glimpses of her inner thighs would keep his eyes glued onto her until he could see them again, mind awash with speculation as to what was concealed beneath her panties.  Ben had stopped denying that he was sexually attracted to his cousin, especially since his prank had gone horribly right, though he tried telling himself that anyone would be no matter the blood relations, she had simply become too sexy. Gwen raised her arms in a yawn and Ben’s shorts grew terribly tight the instant, pits covered in beautiful orange hair were revealed to him and he gripped the remote so hard it could have shattered. For his own sanity Ben knew he'd have to reverse what he'd done or make a move on his cousin, the atmosphere he'd unwittingly created was absolutely stifling and though his hand had kept him company he could only jack off so much in a day. Ben weighed the options in his mind, but his focus returned to Gwen every time before he finally left the room entirely, needing solitude to keep himself focused. 

Gwen smirked to herself as Ben left the room, her sudden hair growth was bizarre but after she’d spent a few days thinking on it and regaining her composure it was obvious that Ben had done something to her. It was impossible to say what he had done, but this was not the kind of thing that just happens, and she had gotten very familiar with the face he makes anytime he does something he isn’t supposed to. At first she had wanted to blab to Grandpa Max immediately, but then she realized her hair was making her cousin act even odder than usual. Her first guess was that Ben was even more grossed out by her body’s new condition than she was, and as such it only seemed fair to make him suffer for what he’d done and show off as much skin as she could around him, but she soon realized the opposite was actually the case. That spaz was even weirder and grosser than she had first suspected, he was getting off on her body hair, and though the thought was sickening it was obviously causing him more discomfort than it was her. In fact, as time went on she’d come to embrace the changes he had caused in her body and if it did in fact disgust him then it only served him right for causing all of this in the first place.

Regardless, Summer was ending and Gwen needed to give Ben a taste of karma for trying to make a fool of her. Gwen had bought a bikini for this vacation specifically and though her parents would kill her if they had seen it, she had managed to smuggle it along. Until now she had had no reason to wear it unfortunately but she was happy that she’d get at least some use out of it even if she wouldn’t be turning any heads at the beach. It left little to the imagination and considering her dad was barely okay with her wearing a standard two-piece swimsuit it was very fortunate she had managed to keep it a secret from him. Micro-bikini was  _ almost  _ too generous of a description, the smallest top imaginable covered her nipples though the edges of her areola were very much visible and the bottom, well, what bottom? The stripe of cloth could barely cover her vagina and it was obscured even further by her orange forest. She would at least turn her cousin’s head whether it was in disgust, or with desire, as she suddenly imagined. That dirty thought was ignored, though on an completely unrelated note, her rock hard nipples were threatening to poke out of her top. Setting those... _obscene_ thoughts aside, Gwen planned her ambush.

It was their last day at their Grandpa’s, and luckily Max would be out until the evening, Gwen slipped her swimsuit on and inspected herself in the mirror. It was almost more embarrassing than just being naked, but she knew that she was rocking it, enjoying the opportunity to have her bush and the trail that ran up her navel on display. Max had only just left the house and though it was almost noon, she suspected that Ben was still asleep, having taken to sleeping in rather than fight her for time in the bathroom. Just as she was getting bored reading on her bed Gwen heard Ben’s door open down the hall and the bathroom door shut immediately after. Gwen smirked and quietly opened her door and slinked out of it to prepare the ambush. As silently as possible Gwen turned Ben’s doorknob and ran inside, shutting it as carefully as possible. As expected, Ben had turned to room into a pigsty, probably having never even thought of cleaning it all summer. Stepping forward,  Gwen nearly shouted in surprise as she tripped over Ben’s ratty sneakers, falling face forward into a pile of laundry which at least managed to break her fall even if not in the most dignified way. Pulling her face away from her cousin’s dirty skivvies, Gwen inhaled without thinking about the situation, inadvertently catching a whiff of his shorts. 

  
“Blehh, gross…” Gwen bemoaned, as if telling herself that she should find it gross to make her actual reaction more palatable. The idea that the musky boyish scent had turned her on ever so slightly was an anathema to her.

Hurrying back up Gwen moved beside his door and tried to control her breathing. Her heart was racing, it wasn’t every day you exposed yourself to your cousin, but as she kept telling herself this was his own fault. The toilet flushed and the bathroom door opened, Gwen bit her lip, holding her breath and trying to calm her rapid heart rate. Ben’s door was swung into Gwen’s face and she had to hop backwards to keep it from slamming into her. As the still sleepy Ben shambled in Gwen slammed the door shut behind him and stood at attention in front of it.

“G-Gwen?!” Ben jumped in surprise, his eyes quickly focusing on his cousin’s body before he averted them, his face turning a deep red.

“Wh-What’s wrong DWEEB, did your plan work too well?” Gwen asked as she cocked hips to the side and flaunted her new hairy body, confident she'd either disgust or rile up her annoying cousin. 

“I don’t know what you’re talking about.” Ben insisted, his eyes locking onto Gwen's own as he tried hard to keep them from wandering.

“You really think I’m gonna believe that, let alone Grandpa Max? I’m sure there’s some freaky alien in that watch of yours that could cause this.” Gwen accused, pulling her arms up to show off her pits in an exaggerated stretch that made Ben avert his eyes once more.

“What’s more likely, that I used the Omnitrix just to pester you or that you can’t bother to pick up a razor?” Ben countered.

“I don’t know, but how about you tell me this: what’s he going to be angrier about, that you did this to me or that you did it just to beat off to your cousin’s body?” Gwen asked in smug satisfaction, knowing that whether or not that was true it would get quite the reaction out of him.

“I DID NOT!” 

“Ah-ha! So you admit that YOU did this.” 

“I-I did not! And who would think a-a frikkin’ werewolf like you is sexy?!” Ben yelled defensively.

“Oh so I guess it’s someone else’s….THING that’s pitching a tent in your pants!”

Ben’s face flushed again and tried in vain to cover the crotch of his pajamas. Gwen’s face was bright red in a mixture of embarrassment and anger, had she really misread the circumstance and she was in fact ugly? If so then why was her cousin so hard, and if she was just trying to shame her cousin than why was the thought of her cousin’s penis driving her up the wall? 

“A-Admit it, you started all of this so you’d have some eye candy around the house this summer!” Gwen bristled as she stepped toward her dumb cousin and reached for his arms, trying to wrest them away from his crotch to expose his shame. 

“Get OFF of me you, you, amazon!” 

Ben may have been the stronger of the two but his embarrassment stifled any real resistance and when Gwen pushed against him he fell like a stack of cards and she toppled over with him, refusing to let go of him. As Gwen tumbled on top of him she pinned his wrists besides his head, no stranger to wrestling with Ben, and peered beneath her as she straddled his waist to prove how much of a pervert he was. To Gwen’s shock her cousin’s dick had slipped through his open fly, and stood still, the only motion coming from the clear stuff dribbling out the tip and the occasional jump as blood pumped into it.. Gwen could feel her body reacting to the sight, pussy creaming as the swelling of her lips obscured her bikini bottom even further. Her nipples pressed against the small patches of fabric which covered them, hardening as she began to realize the situation she had gotten herself into.  Ben’s face remained red, chest heaving with nervousness as he watched his cousin stare at his cock. The idea of Gwen reciprocating his feelings of deep sexual attraction was too good to be true, but he couldn’t help but consider it as she continued to stare at his manhood.

“You, you-uh-*cough* re-really like all this hair huh…” Gwen asked in a distant tone of voice, both hands removed from her cousin as her fingers gently ran through the hair on her happy trail.

“You really are a p-pervert…” Gwen continued to chastise, one of her fingers tugging at one of her bikini's straps absentmindedly. 

Ben kept quiet for once, watching as an unusual change came over his cousin, her cheeks were redder than he’d ever seen and seeing her all worked up, nipples poking through her bikini top, it was only making him hornier. Gwen glided her hand along Ben’s bare side and down his thigh, stopping just short of his shaft as she considered what she was doing. For a moment her hand hung midair, as both cousin’s held their breath in anticipation, would they cross that line, or would Gwen refuse and never speak of this again. Finally and firmly, Gwen gripped Ben’s cock, her soft hands feeling completely alien in comparison to Ben’s own familiar touch. Gwen’s bit down on her lip as she began to move her hand with some trepidation, watching as the loose skin rolled up and down his pink head. 

Gwen was hardly an innocent virgin, though virgin she very much was, she had seen porn, she knew what was done and how it was, but her heart was beating harder and harder as she got used to the heat radiating from Ben’s cock. It didn’t take long for Gwen to start getting creative with her stroking, her grip loosening as she ran her fingers up and down his length, and eventually running down to his soft balls. As she took things further Gwen was only getting wetter, she could feel a powerful yearning that needed filling between her legs and the sounds of Ben’s soft moans did not help anything. Reluctantly she removed her hand from Ben and untied the knots keeping her bikini on, allowing the swimsuit to fall onto Ben beneath her as she raised herself off of him.

“Look what you did...Dweeb…” Gwen said, attempting to scold him, but her voice was too soft and shaky.

Her pussy was a bright pink, her labia slightly spread by themselves, and all crowned by an almost dainty clit. Ben had to consciously keep himself from drooling as he saw what he had been fantasizing about for weeks in person, and surrounded by a vibrant and healthy bush that he wanted to shove his face into more than anything.

As if reading his mind Gwen spoke up, “You’d  _ better  _ take care of this.” she commanded, managing to get a bit more authority in her tone.

Without waiting for his response Gwen shoved her crotch into his face, and without skipping a beat Ben began to eat her out, salivating madly as he did so. Ben was...amateurish, but neither knew much better and Gwen was so riled up that about anything felt really good. His tongue lapped desperately at her slit, running up and down as he savored her natural taste while his saliva and her quim mixed and ran down her thighs and his cheeks as he got sloppy and sloppier. Gwen constantly pushed her hips down harder and harder, wanting to feel his tongue as deeply as she could. 

“Mmm, Fuck…” Gwen moaned as Ben’s hands gripped her thighs. He held her down while he shoved his tongue into her, the tip wiggling as deep inside of her as he could get and driving her up the wall.

Gwen bit her lip to keep from crying out and pressed her hand against his forehead, pulling her pussy away from his mouth as she sat up above him. Gwen’s finger slid up her slick vagina and she inspected her finger and just how obscenely wet she had gotten. She looked back at Ben beneath her as she began to process what they were doing, was it too late to back away now? Ben answered the question for her, raising himself up beneath her and allowing her to fall back down onto his floor. Ben kneeled over Gwen now, reversing their positions, and took a new unashamed gaze at her. Her shapely body made all the more attractive by what he had expected to be unsightly body hair. Beautiful bright orange hair punctuated Gwen’s body, running down her legs and her inner thighs and of course creating a beautiful bush and covering her underarms. 

Ben spread Gwen’s legs for her and fit himself between them, his shaking hand trying to guide his cock into her. After a few more seconds of him futilely trying to find the hole Gwen sighed and lifted her hips, finding his cock with her hole rather than the other way around. As Ben slid inside of her Gwen gasped in shock, deciding immediately that her fingers would never be able to pleasure her again and Ben was himself coming to the same conclusion. The two didn’t bother taking anything slow, both cousin’s hips immediately moving against the other, Ben thrusting into her while Gwen’s own hips gyrating against the rod piercing her. Ben fell atop her almost immediately, holding her body close to his while she flung her arms around him to return the favor. 

Ben left a clumsy off-center kiss on the edge of Gwen’s lips, hesitant to kiss his cousin despite already being balls deep inside of her.

“You freaking dweeb…” Gwen sighed in disappointment, grabbing the back of his head to force his lips to hers, their tongues colliding against the other in an inexperienced brawl. 

Gwen lifted her hips, throwing her legs around her cousin, the feeling of his body against hers being all too natural and satisfying to resist. Ben’s hand ran down Gwen’s side, taking in the sloping of her natural curves; his mind was filled with questions and worries but he pushed them aside and focussed on the moment at hand. Ben couldn’t believe how Gwen’s pussy seemed to squeeze his cock in all the right ways, as if made to fit his penis specifically. Ben didn’t tend to think things through and that was most true when he was excited, so when he felt his orgasm coming it never even occurred to him to pull out or warn Gwen. 

“Yes, Gwen! Fuck yes!” Ben exclaimed, the closest thing Gwen would get to a warning as Ben forced himself as deep as possible and came. 

Gwen herself wasn’t even upset at first, cooing into Ben’s ear as she felt him fill her; she did not even register that the warmth she was feeling was her cousin’s cum shooting into her, but her toes curled regardless as she embraced the feeling. Ben sat there on top Gwen, their chests heaving against each other as they slowly came to grips with what they’d done. Ben made the first move, lifting himself off of Gwen and pulling out, watching his cum spill out of her orange hairy muff with childlike glee. 

“What’re you...BEN did you...do  _ that  _ inside of me?!” Gwen asked.

“Uh, what do you-?”

Gwen got up, heart sinking as she saw her snatch oozing with a warm white fluid.

“Ben you IDIOT, what’re you going to do if I get-” 

Gwen was cut off as the front door creaked open and Grandpa Max shut it behind him.

“Alright kids, it’s packing time!” 

Gwen opted to ignore the pregnancy scare for the moment to try and find something of Ben’s that she could wear that was at least half-clean, there would be plenty of time to get back at Ben for all the stupid things he’d put her through Her new hair though? He’d gotten his reward for this marked improvement to her already sexy bod, and she was already thinking of all the fun the'd be having AFTER she paid him back for this unwanted creampie


End file.
